Automatic erasing typewriter system

ABSTRACT

A typewriter having a character erase mechanism is combined with an automatic control system including a changeable memory that maintains a record of both characters printed and characters erased to enhance the typist&#39;&#39;s ability to edit and correct text as it is typed. With this system the typist can select automatic erasure of individual characters, selected words, or an entire line simply by depression of a key. Furthermore, typist can add, delete or correct words as desired and the typewriter will automatically reprint correct text that was erased to enable such insertion or deletion.

United States Patent 1191 [111 3,780,846 Kolpek et al. Dec. 25, 1973[54] AUTOMATIC ERASING TYPEWRITER 3,200,740 10/1965 Schaller et a1197/172 X SYSTEM 3,204,745 9/1965 Wolowitz 197/181 x 3,204,746 9/1965Wolowitz.... 197/151 X [75] n en Robert p Robert 3,270,852 9/1966FOlld1llB1'..... 197/181X Rahenkamp, both of Lexington, Ky. 3,397,7678/1968 Hobbs 197/181 3,414,103 121968 K d t 1.... 19720 [731 Asslgneellmemamna' Bus'ness Machmes 3,595,362 7/1971 197/l81 x Corporation,Armonk, 3,630,336 12/1971 Johnson et al 197/19 x [22] Filed: Aug. 3,1972 Primary Examiner-Emest T. Wr1ght, Jr. [21] Appl. No.: 277,718Attorney-E. Ronald Coffman et a1.

[52] US. Cl. 197/19, 197/113, 197/181, [57] ABSTRACT 340/1161 R Atypewriter having a character erase mechanism is [51] I111. Cl. B41] /30combined with an automatic control system including [58] Field of Search197/16, 19, 20, 113, a changeable memory that maintains a record of both197,151 340/1461 R characters printed and characters erased to enhancethe typists ability to edit and correct text as it is [56] ReferencesClied typed. With this system the typist can select automatic UNITED SATES PATENTS erasure of individual characters, selected words, or an1,183,424 5/1916 Baldwin 197/181 ntir line simply y depression f a key.Further- 1,399,734 12/1921 Baldwin 197/181 X more, typist can add,delete or correct words as de- 5,293 5/1922 Baldwin 181 sired and thetypewriter will automatically reprint cor- 3 1 l/1946 33mm? 197/181 Xrect text that was erased to enable such insertion or 3,278,897 12 1962Ashby et 31.. 340/146 1 R deletion 3,149,711 9/1964 Wolowitz.....197/151 X 3,154,183 10/1964 Wolowitz 197/181 X Claims, 11 DrawingFigures 1 OPERATION 51 sEuuERcER 46 ERASE KEY STROKE UPPER LIMIT ER11111. R 1:11.11. BY 8 UPDATE TERMINATION Eg 2 REGRESS BYONE 44GENERATION l M 9 LOWER 111111 75 ws READ READ Z QUEUE'IN WRITE RTE PRINTRETYPE w 1 5 5 l rr wRnE 1 82 2 61 'ii'ii 85a 64 RETYPE 2 m2 ERASE YFwBLE A -1 EWBJ 1 ONLY CURRENT PRINT SECONDARY ERASE SW. 0 POSITION W-,WORD 62 3/ ERAs R11 GT 1 63 61/ REGlSTER KEYBOARD OUTPUT Q KEY STROKE 3sRETYPE 66/ STORE 42 I i i L- f, MEMORY ouEuE 00111101 7} g 4ollUl1llll-mfiBL ..U[l|l|]ll|l PATENTEU 3.780.846

- SHEU 2 or 9 r fimfi m SPACE BAR CHARACTERS 3 WRITE KEY INFO.

STORE CURRENT PRINT POINT READ QUEUEI) BYTE FROM MEMORY T0 MEMORY V0REG.

IS "SYMBOL NOT APPEAR" IN MEMORY I/0 REG.

ouEuE CONTROL nor AT UPPER LIMIT T0 100 To 0 KEY STROKE T0101 V MEMORYRECORD QUEUE OUT SEQUENCE V SEQUENCE FIG. 4 FIG. 5

PATEMYE [E02 5197:

SIEEIZBFQ' FIG. 9

FIG. 4

FROM 94 N0 4 3mg,

YYRYYE KEYBOARD 101 :REG. BYTE T0 ouEuEB MEMORY ADVANCE ouEuEB CONTROLBY ONE RESET KEYBOARD REG. T0 EMPTY END PAIiNIfnnzczsma v 3.780.846

SHEET t Of 9 FIG. 5

FROM 94 YES SET OUEUE CONTROL 0 T0 UPPER LIMIT READ OUEUEO CONTROL H2FROM MEMORY TO MEMORY l/O ADVANCE OUEUE CONTROL BY ONE WRITE MEMORY I/OBYTE TO OUEUED MEMORY RECRESS OUEUE CONTROL 115 BY ONE OUEUE CONTROLPRINT POINT PAIENIEDUECZSIHH $780,846

SHEE! 5 0F 9 ERASE START FIG. 6

SET ERASE 15o MODE READ OUEUED BYTE 51 FROM MEMORY T0 MEMORY V0 REG.

PRINT CONTROL SEQUENCE v amas;

QUE E00 0L T0 150 To BY ONE MEMORY UPDATE 1 SEQUENCE FIG.8 BACKSPACE TWOPRINTER SELECTIVE I T0 185 TERMiNATION SEQUENCE FIG. 10

RESET 15s ERASEONLY RESET 154 ERASE MODE PATENTEDnzczsrsm FROM 152 YESSMEU 6 OF 9 SYMBOL UNDERSCORED FIG. 7

148\ SHIFTTSRINTER UPPER CASE L T PRINT v UNDERSCORE PRINT SYMBOL ANDMEMORY I/O REG.

PAIENTEDBEI325I9Y5 3.780.846

SHEET 7 BF 9 FROM 185 YES FROM 445 FIG. 8

15 165 v WRITE WRITE "N0 mm." "SYMBOL NOT APPEAR T0 ToouEuEo I OUEUEDMEMORY MEMORY Y 152 ADVANCE ouEuE CONTROL BY ONE U+E TE READOEU DBY FROMMEMORY To MEMORY V0 REG.

155 I60 "NOINFO" RETURN ouEuE CONTROL IN MEMORY V0 REG To PRINT POINTTRTRTRRR ESSES ouEuE CONTROL MEMORY V0 REG.

BY ONE v 461/ R i WRITE MEMORY I v ll-O BYTE T0 ono OUEUED MEMORYPATENTEB 3.780.846

' SHEEI 8 OF 9 FIG. 10

r as E OUEUECONTROL AT LOWER LIMIT REGRESS OUEUE CONTROL. m

BY ONE v 4 r TRANSFER OUEUED BYTE n4 RESET T g g LINE LATCH l3 n I -4s4y WORD LATCH 5 FROMBZ'NO IS- n6 1N0 v "SPACE"IN \\\YES N YES MEMORY I/OWORN/0 To N0 ERASEWO YES y r a W- I CLOSED,

' SET LINE LATCH Tom 52 RESET WORD LATCH ITO PATENTEDOECZSIBH RETYPESEQUENCE RETYPE Y/ saw 9 m 9 FIG. 11

SET RETYPE MODE READ OUEUED BYTE FROM MEMORY TO MEMORY V0 REG.

IS SIGNIFICANT INFO. IN MEMORY V0 REG.

DELETE "SYMBOL NOT APPEAR" FROM BYTE m OUEUED MEMORY SPACE PRINTER PRINTCHARACTER comm "UNDERSCORE" Y ADVANCE OUEUE -207 CONTROL BY ONE 1AUTOMATIC ERASING TYPEWRITER SYSTEM CROSSREFERENCES Cross reference ismade to US. Pat. 3,724,633 and to co-pending applications, Ser. No.102,696 to S.A. Okcuoglu, R.V. Davidge, C]. Davis, and 1.0. Schaefer,filed Dec. 30, I970 and entitled Automatic Erase Mechanism and Ser. No.266,764, to R.W. Lehnhardt and J0. Schaefer filed June 27, 1972,entitled "Erase Ribbon Feed. These documents disclose structure by whicha typewriter is given the capability of effectively erasing individualcharacters either by the use of an adhesive tape to lift the inked imageof a character from a page or through the use of a white cover-uptransfer ribbon for masking the character so as to no longer be visible.

BACKGROUND OF THE INVENTION Effective typing speed has been increasedthrough the use of typing systems having magnetic memory that allow atypist to simply restrike a correct key over an incorrect character.Following initial keying of text and the correction of errors, therecord is then played out onto a clean sheet of paper to show only thecorrect text. More sophisticated systems enable the typist to insert ordelete information that is recorded in a memory together with originallytyped text which then is played out to produce final copy that is freeof errors. Specially configured text editing systems employing cathoderay tube displays combined with bulk storage memories have beenproposed. While these systems are quite versatile in the editingpermitted the typist, their output is again some form of record thatmust be played out to produce finished error-free copies.

The patent and applications identified in the Cross- References sectionabove disclosed mechanism by which a typewriter is given the capabilityof erasing characters from a page. A typewriter equipped with suchmechanism can be operated manually by a typist to erase characters oneat a time from the page. The material erased can then be re-keyedcorrectly. Upon completion of the page, errors have been corrected andthere is no need for a further play out operation. While manuallycontrolled erasure and retyping is quite adequate for those errorsdetected within one or two keystrokes of their occurrence, errors suchas character or word omission may involve such a large number of manualoperations to correct that the operator would prefer simply to retypethe page rather than attempt to correct it.

To assist a typist in gaining the full value of a character erasecapacity within a typewriter, we have devised a control system for thetypewriter including a memory capable of recalling characters and otherinformation previously typed as well as whether such informationcurrently appears on the printed page or has been erased. Havingprovided this basic capability, the versatility of the moresophisticated text editing systems employing non permanent displays suchas a cathode ray tube display can be incorporated into a simple typingstation. With our system it becomes both possible and practical for thetypist to make corrections involving addition or deletion of words orletters anywhere within an operative segment of text such as the currentline in which the typist is operating.

Our system is particularly important where the erasing mechanismrequires for its operation restriking of an erroneous character. Sincethe characters originally keyed are recorded in the memory, a simpleinstruction to erase is automatically translated into the sequencenecessary to re-select a print operation of the erroneous pre-recordedcharacter with the typewriter adjusted to perform an erase rather thanprint operation. The same sequence performed manually requires theoperator to select erase and then manually re-key the erroneouscharacter.

DISCLOSURE OF THE INVENTION As briefly indicated above, our inventionrelies on a memory that is capable of recalling characters previouslykeyed and whether those characters currently appear on the printed pageor have been erased. The memory can be conceptually divided into aplurality of bytes or cells made up of multiple digital storage bitscapable of identifying what symbol is intended to be printed includingwhether the symbol is printed from upper case or lower case on thetypewriter and whether it is modified as by an underline or accent. Thebyte or cell also should be capable of recording a space in place of aprintable character. To accomplish our invention, the byte shouldfurther be capable of indicating the presence of significant informationwithin the byte and whether that information currently is appearing onthe printed page or has been erased. Such bytes or cells within thememory are ordered to correspond with ordered print positions within atext segment such as a line. Having provided this memory capacity, eraseoperations are produced upon selection of the typist and under thecontrol of sequence generating circuitry and the character identifyinginformation within the memory. Depending upon whether the characterserased are desired to be reprinted or are to be deleted entirely, thememory is updated by recording respectively the fact that a desiredcharacter does not appear on the printed page or, in the case of adeletion, that a previously recorded byte no longer contains usefulinformation.

To facilitate deletions, queue-in sequence circuitry is provided andoperates upon deletion of a character to move higher order erasedcharacters into the deleted position within the memory order.

To facilitate insertions, queue-out sequence control circuitry isprovided for moving recorded erased characters in the memory to higherorders within the memory order as the typist retypes new, unrecordedcharacters into erased location corresponding to erase characters to beultimately printed.

Having completed a correction, the typist can return automatically towhere the normal typing was interrupted simply by striking a retype keyto operate retype sequence circuitry provided in our system thatoperates under control of the character identifying data within thememory to reprint those erased characters marked to be reprinted and, inthe event that printed characters are recorded and remain printed on thepage will simply space the print point without restriking thecharacters.

These and other objects, features and advantages of our invention willbe made more apparent to those skilled in the art by the followingdescription of a specific illustrative embodiment wherein reference ismade to the accompanying drawing of which:

FIG. 1 is a block organizational view showing the primary componentsemployed in the preferred embodiment of our automatic erasing system;

FIG. 2 is a diagramatic representation of the memory organization to beemployed in the automatic erase system of FIG. 1;

FIG. 3-5 are an operational flow diagrams of a keystroke record logicsequence illustrating the necessary details required for one skilled inthe art to configure the specific circuitry to be incorporated in thesystem of FIG. 1; I

FIGS. 6-8 and are operational flow diagrams showing an erase logicsequence illustrating the necessary details required for one skilled inthe art to configure the specific circuitry to be incorporated in thesystem of FIG. 1;

FIG. 9 is a side elevational view of an erase key constructed inaccordance with a preferred embodiment of our invention; and

FIG. 11 is an operational flow diagram showing a retype logic sequenceillustrating the necessary detail required for one skilled in the art toconfigure the specific circuitry to be incorporated in the system ofFIG. 1.

Referring now more specifically to the drawing, in FIG. 1 there is showna typewriter 10 such as the IBM SELECTRIC I/O Typewriter manufactured byInternational Business Machines Corporation, Armonk, NY. and describedin Customer Engineering Manual of Instruction Form Part No. 241-5159-3,published May, 1962. This typewriter 10 has the capability of generatingelectrical signals representative of the keyboard action and further hasthe capability of operating from electrical input in addition tooperating from keyboard input. Although a full set of typewriterfunctions can be performed by the typewriter 10, those of primaryinportance to our invention are the character-bycharacter printingmechanism 11 that prints an inked symbol 12 at a print point 13 on apage 14, an escapement or letter feed mechanism 15 for moving the printpoint 13 rightwardly to successively higher order print positions 16,17, 18, etc within a writing line 19, and a backspace mechanism fordisplacing the print point 13 rearwardly or leftwardly to successivelylower order print positions along the writing line 19. In addition, thetypewriter 10 includes shift mechanism 21 to select printing of upper orlower case characters and nonprint mechanism 22 like that of U. S. Pat.No. 3,592,309.

The typewriter 10 includes a keyboard 30 having a group of characterselecting keys 31, a spacebar 32 for controlling the escapementmechanism 15 independent of character printing, a backspace key 33 forcontrolling the backspace mechanism 20, a shift key 34 for controllingshift mechanism 21, a line return key 35 for returning the print point13 to a left margin position and feeding the page 14 upwardly to a newwriting line, and a tabulation key 36 for moving the print point 13 in acontinuous run rightwardly along the writing line 19. The operation ofthe keyboard 30 generates electrical representative output signals onlines 37, including data lines 38. Input signal lines 23 deliver controlelectrical signals to the typewriter 10 for controlling its operation.

The typewriter 10 is also provided with a print ribbon feed mechanism 24which preferably is like that disclosed in U. S. Pat. No. 3,604,549 andsymbol erase mechanism including erase ribbon handling mechanism 25 likethat described in aforementioned US. Pat. No. 3,724,633. The eraseribbon handling mechanism 25 responds to counter-clockwise pivoting of abail 26 from its position as shown to lift an erase ribbon 27 intoalignment with the print point 13 while the printing mechanism 11restrikes the image of the symbol 12 to be erased. The erase ribbon 27is wound incrementally to present a new ribbon surface for each erasingoperation. The erasing ribbon 27 can have either a white cover-uptransfer layer for camouflaging an erroneous character or an adhesivelayer for lifting the ink of the erroneous character from the page 14.In either case the symbol 12 is effectively erased by printing on theerase ribbon 27.

Since it is ordinarily desired to reprint a correct symbol 12 in thespace from which an incorrect character was erased, the bail 26 isconnected by link 28 to the escapement mechanism 15 to cripple theescapement mechanism 15 during an erase printing operation. Anelectromagnet 29 is connected to the bail 26 for pivoting the bail 26 toits active position upon receipt of a suitable electrical signal.

The system shown in FIG. 1 further includes a bulk information store ormemory 40 for recording symbol information identifying bytes 41corresponding to individual print positions and recalling these bytes 41in ordered sequence according to the progression of print positions 13along writing line 19.'FIG. 2 shows a somewhat simplified example of thecontent of an individual byte 41 of storage within memory 40. Byte 41includes eleven binary storage bits labeled respectively B1 through 811.The bits B1 through B9 are employed to identify the symbol l2 intendedto appear on the page 14. Of these bits, bit B7 defines whether acharacter to be printed is in upper or lower case. Bits B1 through 86identify the particular character within the selected case. Bit B8identifies whether the character identified also includes an underlinein the manner for example, as is disclosed in U. S. Pat. No. 3,630,336.Bit B9 indicates whether the character is to be printed or simply is aspace such as an interword space. Bit B10 identifies whether the entirebyte 4] contains useful information or is empty. Bit B11 indicateswhether the identified symbol 12 currently appears on the page 14 orwhether it has been erased and is awaiting reprinting. As indicatedabove, the configuration of byte 41 is somewhat simplified for purposesof explanation. While individual bit storage is shown for identifyingwhether useful information is present, whether the symbol 12 is a spaceand'whether the symbol 12 is currently printed, it will be appreciatedby those skilled in the art that this information can, if desired, beencoded to reduce the total number of bits required to store anequivalent amount of information. While we prefer to employ a monolithicmemory that provides for byte storage in printed circuits, it will beunderstood by those skilled in the art that any from of bulk memory suchas core memory, or even to a limited extent, magnetic tape can beemployed in place of the monolithic memory we prefer.

The memory 40 includes sufficient capacity for the largest number ofanticipated print positions within a selected text segment. We prefer toselect the writing line as the text segment within which corrections areto be made and thus provide preferably 128 bytes of storage in thememory 40 which slightly exceeds the number of print positions in mostnormal writing lines. The memory 40 is coupled with a memory gueuecontrol or addressing device 42 which maintains control of the order ofbyte 41 within the memory 40. As the state of the art is well developedin the structure of a memory such as required for memory 40 andaddressing systems as required for memory gueue control 42 the detailsof these elements will not be developed herein. It is sufficient to knowthat the memory queue control 42 can identify the byte 41 in sequenceand can progressively identify those bytes either in increasing order ordecreasing order by corresponding changes of the numericalidentification. To select different bytes, signals can be generated online 43 to advance the gueue control 42 by one and on line 44 to regressthe gueue control 42. The current status of gueue control 42 can be reador a completely new status written through lines 45. The gueue control42 indicates its upper limits by a signal on line 46 and its lower limitby a signal on line 47.

To inter-relate the operation of typewriter with the memory 40 there isprovided a control system 50 constructed of interconnected circuitrywhich can be divided for the understanding of those skilled in the artinto an operation sequencer or clock 51, a condition store 60 fortemporarily retaining information concerning various conditions ofoperation necessary for control of the operation being processed, andcombinational logic 52 for making sequential decisions and issuingsequential control commands in an order determined by the operationsequencer 51 based on information present in the typewriter 10, thememory 40, and the condition store 60. Suitable operational circuitryincluding output signal generating circuitry 53 for issuing the desiredtypewriter control command signals, and memory read-write circuitry 54operating through lines 55 is also provided. As an object of ourinvention is to increase the versatility of the simple typing station,we prefer to employ self contained wired circuitry. As the details forconfiguring specific circuitry to accomplish prescribed decisional andcommand functions is well known to those skilled in the art and do notin and of themselves constitute part of our invention, such circuitry isnot herein described. It is to be understood that instead of specialpurpose wired circuitry as we prefer, the functions to be performedcould be accomplished through the use of a suitably programmed generalpurpose computer.

The condition store 60 portion of our interconnecting circuitry 50includes so-called latch circuits capable of storing both mode controlinformation and character identifying information. More specificallybistable erase latch circuit 61 is set to initiate an erase se quence inresponse to an electrical signal on primary erase switch line 61a. Wordlatch 62 is set in response to an electrical signal on secondary eraseswitch line 62a and indicates whether or not an erase sequence is to beof word unit length. Line latch 63 is set by an electrical signal onsecondary erase switch line 62a being maintained through the completionof a word erasure to indicate that an erase sequence is to be of lineunit length. An erase sequence of a single printed character only isindicated by setting of erase latch 61 without setting the word latch 62or line latch 63. Latches 61, 62, and 63 thus combine to define threeeffective states, namely line erase if latches 61 and 63 are set, word"erase if latches 61 and 62 are set and latch 63 is not set, andcharacter erase if only latch 61 is set. Erase only latch 64 is set byan electrical signal from erase only switch line 64a to indicate thatcharacters erased from a page 14 are to be retained in memory 40 forlater recall in order that they may be reprinted. The normal state oferase only latch 64 is to select erase and delete operation whereincharacters erased from a page 14 are at the same time purged from memory40. Retype latch 65 is set by an electrical signal on retype switchline65a and indicates whether or not a retype sequence is in progress.

In addition to the individual condition latches 61 through 65 thusdescribed, the condition store 60 further includes several registers forretaining multi-bit information required for control of the process.These registers include a keystroke store register 66, a memoryInput/Output register 67, and a current print position register 68.Keystroke store register 66 is connected with keyboard data output lines38 and records a byte of information corresponding at least to theinformation contained within bits Bl through B9 of the storage byte 41in memory 40. Memory Input/ Output register 67 is connectable with thememory 40 under the control of memory queue control 42 to receive asingle byte 41 of character identifying information therefrom or towrite a single byte of character identifying information thereinto.Memory lnput/Ouptut register 67 is further connectable to the outputsignal generating circuitry 53 to control the typewriter 10 to performcharacter print operations either for reprinting or for erasing and forcontrolling space operations. Current print position register 68 isconnectable through read-write circuitry 54 with the memory gueuecontrol 42 to record the current print position of the typewriter 10 andto reset the memory gueue control 42 as desired to correspond to thecurrent print position.

The combinational logic 52 includes groups of circuitry for performingthe various control sequences of our invention including decisionalcircuitry connected with the typewriter 10, the memory 40 the memoryqueue control 42, and the condition store 60 at discrete times asdetermined by connections with operation sequencer 51 to determinewhether or not at that time a particular condition pertains. Circuitryis also provided for controlling the generation of control or commandsignals and conditions for causing the various operations of thetypewriter 10, the condition store 60, the memory queue control 42 andthe memory 40 to occur at times determined by connections with theoperational sequencer 51. The specific electronic components and theinternal wiring necessary to make these decisions and effect thesecommands is well within the state of the art and can be constructed withonly routine design effort given knowledge of the decisions to be made,the operations to be effected, and the sequence of these decisions andoperations. Accordingly, we have shown the circuitry as grouped intoseparate primary sequence control sections namely, keystroke recordsequence control circuitry 56, erase sequence control circuitry 70 andretype sequence control circuitry 80. The keyboard record sequencecontrol circuitry 56 further includes memory queue-out or advancesub-circuitry 57 and detection logic circuitry 58 for determining thepresence or absence of symbol not appear" bit B11 in memory I/O register67. Erase sequence control circuitry 70 further includes memory updatesequence control sub-circuitry 71 further in- 7 cluding memory queue-inor regression sub-circuitry 72, selective termination circuitry 73 andprint sequence control circuitry 74. The selective termination circuitry73 includes sequence repeat logic circuitry 75, word erase completiondetection logic circuitry 76, line erase completion detection logiccircuitry 77, character erase completion detection logic circuitry 78,and repeat inhibit logic circuitry 79. The retype sequence controlcircuitry 80 shares the print sequence control circuitry 74 with theerase sequence control circuitry 70 and further includes retype sequencerepeat logic circuitry 81 and retype repeat inhibit logic circuitry 82.

The detail of the specific sequence control circuitry is determined bythe sequences to beperformed which are laid out in operational flowdiagrams shown in FIG. 3.

A keystroke record (see FIGS. 3 through 5) is initiated by the typistdepressing one of the character keys 31 or the spacebar 32 of thetypewriter 10. While the typewriter l0 proceeds through its ownindependent print and spacing cycle the information keyed is deliveredon output lines 37 and stored by operation 90 in keystroke storeregister 66. The current position of print point 13 along writing line19 is stored by operation 91 in current print position register 68 byreading the current numerical status of the memory queue control 42thereinto. It will be recognized that the current print position can bestored within the typewriter itself by the provision of a print positiontransducer capable of indicating discrete identification of eachprinting position along the line. Operation 92 reads the informationcontained in the byte 41 of memory 40 indicated by memory queue control42 as corresponding to the current print position of the typewriter 10and delivers this information to memory [/0 register 67.

When information is keyed initially in a new line, the operation 92 willplace no significant information in memory I/O register 67. Having thusstored The essential conditions for keystroke recording control, thekeyboard sequence control circuitry 56 determines at decision 93 bylogic circuitry 58 whether the byte of information in memory I/Oregister 67 includes symbol not appear information or in other words,whether the byte of information taken from memory 40, if any, has beenidentified for later reprinting. Again, in the initial keying of a line,the determination based on the absence of information in the memory I/Oregister 67 is negative and the sequence proceeds to decision 100 (FIG.4) wherein it is determined whether there is use ful information of anytype in the memory I/O register 67. In initial typing, no informationwill be in the memory l/O register 67 and the sequence proceeds tooperation 101 wherein the keystroke identifying data in register 66 iswritten as significant information that appears on the printed page14-into the byte 41 of memory 40 then identified by the memory queuecontrol 42. Operation 102 advances the memory queue control 42 by one tocorrespond with the print point 13 of the typewriter 10 following theprint and space operation thereof. The sequence is then terminated byoperation 103 that resets the keystroke store register 66 so that noinformation is contained therein. Logic 52 responds to depression ofcarriage return key 35 or tabulation key 36 to reset the queue control42 to its lower limit and all bytes 41 in memory 40 to empty. If thetypewriter 10 includes a position transducer that will discretelyidentify all print positions within a line, tabulabeen reached. Adetermination that the upper limit has been reached directs the sequenceagain to operation 101 (FIG. 4) to cause the keyed information tosupersede the previously recorded information in the last availablememory byte 41. If as is the usual case the memory queue control 42 isdetermined by decision 94 to be not at its upper limit, the sequenceproceeds to a queue-out sub sequence controlled by circuitry 57 that iseffected to advance the previously recorded but erased byte 41 to thenext adjacent higher order within the memory 40. This sequence begins byshifting the highest order one of the previously recorded bytes to thenext adjacent higher order, and repeating the shifting process until allbytes of a higher order than the current print position have beenshifted. The sequence begins by operation 110 wherein the memory queuecontrol 42 is set to its upper limit. Operation 111 regresses the memoryqueue control 42 by one to address the second highest order byte 41 inmemory 40. In operation 112 the thus addressed byte 41 is read intomemory I/O register 67 for temporary storage. Operation 1 13 advancesthe memory queue control 42 by one and operation 1 14 writes thetemporarily stored bytein memory I/O register 67 into next higher ordermemory byte 41 of memory 40 now identified by the memory queue control42. Operation 115 regresses the memory queue control 42 by one toreaddress the byte 41 in memory 40 from which information has just beenshifted upwardly. Decision 116 compares the memory queue control addresswith the current print position as stored in register 68 to determinewhether the memory queue control 42 is then addressing the byte 41corresponding to the current print position 13. If not, the sequence isreturned to operation 111 wherein the next adjacent memory byte 41 isshifted upwardly in the memory order. Following each shifting, thesequence proceeds to decision 116 and ultimately that decision willindicate that the memory queue control 42 has become realigned with thecurrent print point 13 as stored in register 68. Upon suchdetermination, the queue-out sequence is completed and the sequence isreturned to operation 101 (FIG. 4) whereby the key stroke information inregister 66 is recorded into a now empty byte 41 of the memory 40.

If at decision (FIG. 4) it is determined that useful information ispresent in the memory I/O register 67, the sequence proceeds to decision104 wherein it is determined whether the keystroke store register 66identifies a space. If a space is identified the operator has simplyadvanced the print point 13 and the sequence proceeds directly tooperation 102 to maintain the memory queue control 42 in properalignment with the now advanced print point 13. If, on the other hand,the operator had struck a printing key, decision 104 would transfer thesequence to decision wherein it is determined whether the information inmemory [/0 register 67 is simply a space. If the sequence has proceededto this point, the prior determinations indicate that the typist istyping a new symbol 12 over a previously recorded and not erased symbol12. This is permissable only if the previously recorded and not erasedsymbol 12 is a space which, if so determined by decision 105, returnsthe sequence to operation 101 for recording of the key stroke. If, onthe other hand, the typist is in fact attempting to type one printedcharacter over a character already printed on the page 14, decision 105will transfer the sequence to operation 106 to immediately operate thetypewriter non-print mechanism 22 described above to inhibit thetypewriter printing but not the spacing operation. The sequence isreturned to operation 102 to advance the queue control 42 by one and tooperation 103 to reset the register 66. The typist thus is preventedfrom spoiling the page 14 by keying new characters over previouslyrecorded and not erased characters.

ERASE SEQUENCE (See FIGS. 6 through An erase sequence is initiated bythe typist upon noting that an error has been committed within thecurrent typing line. While in many instances the error will lie in thelast typed character or symbol 12, our system enables the efficientcorrection of errors even within the middle of correctly typed text.Upon noting that an error has been committed, the typist first mustdecide whether the symbols 12 to be erased are to be retained in memory40 or are to be deleted. The normal operation of the system is to botherase the symbols 12 from the page 14 and delete them from memory 40.Thus no action is required by the typist unless the symbols 12 to beerased are to be later reprinted under which circum-,

stance the operator sets a mode control toggle switch 120 from itsnormal Erase and Delete position (See FIG. 1) to its Erase Onlyposition, prior to depressing erase key 121 (See FIGS. 1 and 9).

Referring to FIG. 9,. there is shown a preferred construction of erasekey 121 including a key lever 122 that is biased upwardly by a leafspring 123 against a stop 124 defining a normal inactive position.Beneath the keylever 122 is a primary erase key switch 125 and asecondary erase key switch 126. Also beneath the key lever 122 is adisplaceable downstop 127 that is biased upwardly by a spring 128 to aposition where it defines a clearance 129 through which key lever 122can move without interference. This initial motion of key lever 122 iseffective to close the primary erase key switch 125 but is not effectiveto close secondary erase key switch 126. Further depression of key lever122 against the loading of spring 128 also closes secondary key switch126. These key switches 125 and 126 are operatively connected with eraselatch 61 and word latch 62 by lines 610 and 62a respectively. Closure ofprimary erase switch 125 sets erase latch 61 at operation 130 (FIG. 6)to activate electromagnet 29 within typewriter 10 to pivot bail 26 andthereby select effective lift and feed of the erase ribbon 27 during asubsequent print cycle. As mentioned above, link 28 from bail 26 alsoshifts the escapement mechanism to a non-feed or dead key position sothat forward space increments are not produced as part of a subsequentprint cycle. Erase latch 61 also initiates the erase control sequence.Closure also of secondary erase switch 126 sets word latch 62 toindicate that the erase sequence is to be of an entire word unit length.The sequence proceeds to operation 131 where under the direction ofmemory queue 10 control 42 the symbol identifying byte 41 of informationcorresponding with the current print position of the typewriter 10 isread from the memory 40 into the memory I/O register 67. Decision 132determines whether the symbol 12 thus read into memory I/O register 67is a printable symbol 12 and if so the sequence proceeds to a printsub-sequence under the control of circuitry 74. The print sequence (FIG.7) begins by decision as to whether the information in the memory [/0register 67 is marked at bit B8 to indicate that it has been underlined.If the symbol 12 has not been underlined, the operation proceeds todecision 141 where it is determined whether or not the symbol 12identified in the memory I/O register 67 is marked at bit B7 as beingupper case. If an upper case character is determined, decision 142determines whether the typewriter 10 is presently in 'upper case. If so,the sequence proceeds directly to operate 143 and magnet drivingcircuitry within the circuitry 53 effectively generates and issues aPRINT command to the typewriter 10 by instructing the typewriter 10 toprint the symbol 12 retrieved from memory 40. Due to the prior settingof electromagnet 29 by erase latch 61, this PRINT command is effectivelyan ERASE command to the typewriter 10. If decision 142 had determinedthat the typewriter 10 was not in upper case, operation 144 wouldprecede operation 143 to operate the typewriter shift mechanism 21 tobring the typewriter 10 to upper case before the PRINT-ERASE command isissued. In the same fashion, if the symbol 12 in the memory [/0 register67 was determined by decision 141 to not be upper case, decision 145follows to determine if the typewriter 10 is currently in lower case. Ifso, the sequence proceeds to issue the PRINT-ERASE command at operation143. If decision 145 determines that the typewriter 10 is currently notin lower case, operation 146 follows to operate shift mechanism 21 ofthe typewriter 10 and bring the typewriter 10 to lower case prior toissuance of the PRINT-ERASE command 'at operation 143.

Returning briefly to decision 140, it is seen that if this decisiondetermines that the symbol 12 retrieved from memory 40 into memory l/Oregister 67 includes an underscore identification at bit B8, thesequence is diverted to decision 147 to determine if the typewriter 10currently is in upper case since the underscore symbol 12 is normallyprinted as an upper case character. If the typewriter 10 is not in uppercase, operation 148 is performed to operate the shift mechanism 21 ofthe typewriter 10 to shift the typewriter 10 to upper case. Otherwise,the sequence proceeds directly to operation 149 to issue an ERASE-PRINTunderscore command to the typewriter 10 before proceeding to decision141 described above.

Accompanying the erasure of symbols 12 from the page 14 by issuance ofERASE-PRINT commands as described above, our invention provides memoryupdate Control Circuitry 71 for selectively writing symbol not appear"information in hit 11 of the byte 41 or, where erase and deleteoperation is selected, writing no useful information" into bit B10 ofthe byte 41 thus making that byte 41 available for other recording.Where a symbol is erased and deleted and higher order symbol identifyingbytes 41 remain in the line, automatic queue-in circuitry 72 within thememory update circuitry 71 displaces the higher order bytes 41 toimmediately adjacent lower order locations within the memory 40. Thememory update sequence begins with decision 150 (FIG. 8) as to thecurrent state of erase only latch 64. The normal state of operation iserase and delete which produces a not erase only response to decision150 and direction of the sequence to operation 151 which records bit B10to indicate that the byte 41 identified then by the memory queue control42 is empty and no longer contains useful information.

From operation 151 the queue-in sequence under control of circuitry 72begins by operation 152 that advances the queue control 42 to the nexthigher order memory address. The memory byte 41 thus queued by theadvanced memory queue control 42 is transferred in operation 153 to thememory I/() register 67. Decision 154 determines whether the queuecontrol 42 has reached its upper limit indicating that there are nohigher order bytes in the memory 40. If the queue control 42 is not atits upper limit, the sequence proceeds to decision 155 wherein it isdetermined whether the newly queued byte of symbol identifyinginformation is marked at bit B10 as empty or containing no usefulinformation. 1f decision 155 determines the presence of usefulinformation, the sequence proceeds to operation 156 wherein the memoryqueue control 42 is regressed by one to the immediately adjacent lowerorder byte 41 which it will be recalled is the original byte emptied byoperation 151. The byte 41 accessed at operation 153 is now written inoperation 157 into the newly accessed byte 41 in memory 40 and operation158 advances queue control 42 by one to the next higher order byte inmemory 40.

The sequence is returned to operation 152 and repeated until eitherdecision 154 indicates that the queue control 42 has reached its upperlimit or decison 155 determines that an empty byte 41 has been accessedat operation 153. In either of these events, the queue-in sequence isterminated by diversion to operation 160 which returns the queue control42 to the address identified by the current print position as recordedin register 68. The byte 41 of memory 40 now identified by the memoryqueue control 42 is written into the memory l/O register 67 at operation161 and selective termination sub sequence is performed under thecontrol of circuitry 73. Decision 170 (See FIG. 10) determines the stateof line erase latch 63. If the line erase latch 63 has not been set, thesequence proceeds to decision 171 to determine the state of word eraselatch 62. 1f the typist had depressed erase key 121 to its secondposition wherein both switches 125 and 126 were closed, word erase latch62 would indicate selection of word" erase operation and the sequencewould proceed to decision 172 wherein queue control 42 is examined byline erase completion logic circuitry 77 to determine if it is at itslower limit as would indicate the beginning of a line. If the queuecontrol 42 is not at its lower limit it is regressed by one at operation173 to address the immediately adjacent lower order byte 41. Operation174 reads the newly accessed byte 41 of memory 40 into the memory [/0register 67. Decision 175 again determines the state of word erase latch62 and again, assuming full depression of erase key 121, the sequenceproceeds to decision 176 wherein it is determined by word" erasecompletion detection logic circuitry 76 whether the byte 41 retrievedfrom memory 40 in operation 174, which incidentally corresponds with theposition immediately to the left of the symbol erased at print pointposition 13 in response to the ERASE command issuing from operation 143,is a space. if no space is detected in the memory [/0 register 67, it isknown that at least one further symbol must be erased within the wordand erase sequence repeat logic circuitry causes a BACKSPACE command tobe generated at operation 177 (FIG. 6) to move the print point 13 of thetypewriter 10 leftwardly by one position and the queue control 42 to beregressed by one at operation 178 to maintain its alignment with thecurrent print position. The entire sequence is thus returned tooperation 131 and repeated until decision 176 determines that a spacewas retrieved from memory 40 in operation 174 at which event thesequence proceeds to decision 180 wherein the current state of secondaryerase key switch 126 is interrogated. 1f the typist has maintained key121 in its fully depressed position throughout the erasure of allsymbols and is continuing to hold the key 121 in its fully depressedposition, detection of the closure of switch 126 in decision 180 directsthe sequence to operation 181 wherein the line latch 63 is set. Thesequence returns to operation 177 for further erase repeating. Thus itwill be recognized that the line" erase mode is selected by the typistby maintaining the key 121 depressed through complete erasure of anentire word.

If on the other hand, key 121 had been depressed fully to close bothprimary erase switch and secondary erase switch 126 and then had beenreleased, decision 180 determines that secondary erase switch 126 is notclosed and repeat inhibit logic circuitry 77 causes operation 182 toreset word" latch 62 to its normal state, operation 133 to reset ifrequired erase only" latch 64 to its normal erase and delete state, andoperation 134 to reset erase latch 61 to its normal inactive state.

In the event the typist had depressed key 121 only until it was impededby stop 127, only primary erase switch 125 would have been closed andword" latch 62 would not be set. The initial sequence would proceed asalready described until decision 171 is reached. Interrogation of wordlatch 62 at decision 171 would produce a negative response and thesequence would be diverted to decision 183 (FIG. 10) wherein the byte 41corresponding to the current print position accessed in operation 161 isexamined by character erase detection logic circuitry 78 to determine ifit is a space. If it is not a space then further operation is unneededand the sequence is terminated by repeat inhibit logic circuitry 79 thatcauses operations 133 and 134. if the typist had decided to erase asingle character after having printed the character and struck thespacebar 32, decision 183 would have determined the presence of a spaceat the current print position and repeat logic circuitry 75 effectsoperations 177 and 178 so that the single character will be erased by arepeat of the entire sequence.

If as described above the line erase latch 63 is set by operation 181,the entire sequence will be repeated with decision directing theterminating sequence to bypass decision 171. Decision 172 thus willterminate the sequence when memory queue control 42 is determined byline erase completion logic circuitry 77 to have reached its lower limitwhereupon repeat inhibit logic circuitry 79 effects operation 184 toreset the line" erase latch 63 and terminate the sequence throughoperations 182, 133 and 134. If desired, additional logic can beprovided to respond to a second depression of key 121 during a lineerase operation to reset line erase latch 63. With such provision, aline erase operation can be interrupted by the-typist upon completeerasure of the word in which the key 121 is restruck.

If the typist elects to erase symbols that are correctly written inorder to reach an earlier point in the typing line to insert an omittedword, erase only key 120 is depressed prior to striking the erase key121, the erase sequence operates as previously described with theexception that erase only latch 64 is set. The state of erase only latch64 is detected at decision 150 and the sequence is diverted to operation163 which writes symbol not appear information into bit B11 of the byte41 indicated by the memory queue control 42 to correspond with the printposition of the symbol 12 erased in response to the ERASE PRINT commandfrom operation 143. After operation 163 the queue-in sequence isbypassed and the selective termination sequence is performed bycircuitry 73 as previously disclosed. It will be recalled that finaltermination of any sequence involves operations 133 and 134. Operation133 resets the erase only latch 64 to its normal erase and deleteoperation.

in the event an erase sequence is initiated with the typewriter printpoint 13 at either a word space or an already erased character, decision132 diverts the sequence to decision 185 which determines whether thebyte in memory l/O register 67 is a space" not requiring erasure andupon such determination, the sequence proceeds directly to decision 150.If decision 185 determines that the byte in memory I/O register 67 isnot a space meaning it is empty the sequence is directed by sequencerepeat logic circuitry 75 to operation 177 and 178 to backspace theprint point 13, regress the queue control 42 and re-initiate the entiresequence with operation 131.

RETYPE SEQUENCE (See FIG. 11)

After an error has been corrected, retype key 190 may be struck to setretype mode latch 65 at operation 191 and initiate a retype sequence asshown in FIG. 11 under the control of retype sequence control circuitry80. Operation 200 reads the byte 41 from memory 40 corresponding to thecurrent print position under the control of memory queue control 42 anddecision 201 determines by retype sequence repeating logic 81 whetherthe thus accessed byte contains significant information or by repeatinhibit logic 82 that the thus accessed byte is empty. If the error iscorrected in the middle of a line which was either bypassed bybackspacing or was erased and marked in memory 40 symbol not appear,"decision 201 will indicate that significant information has beenaccessed and the sequence will proceed to decision 202. At decision 202bit B11 of byte 41 is interrogated to determine if the byte in memoryl/O register 67 defines a symbol 12 that is not printed on the page 14due to prior erasure. Detection of a symbol not appear passes thesequence to operation 203 wherein the symbol not appear" notation isdeleted from the byte 41 in the memory 40 as identified by the memoryqueue control 42 as corresponding to the current print position. Thesequence proceeds to decision 204 wherein bit B9 of the byte 41 inmemory l/O register 67 is interrogated to determine if the informationis not simply a space." Determination that the byte is not a spaceinitiates a print sub-sequence under the control of circuitry 74 that isidentical with the print sub-sequence utilized in the erase sequence.This sequence begins with decision 205 which is identical to decision140 to determine whether the byte in memory l/O register 67 contains anunderline indicator in bit B8. The sub-sequence is completed byoperation 206 which is identical with operation 143 except for the factthat the erase mode latch 61 is not set during aretype sequence and thusoperation 206 will cause ordinary printing of a selected character onthe usual ink ribbon. Since the intervening operations within the printcontrol sub-sequence are identical to those previously described inconnection with the erase sequence, they are not shown herein norotherwise described.

PRINT CONTROL Following operation 206, operation 207 advances the memoryqueue control 42 by one to queue the next higher order byte 41 frommemory and the sequence is returned to operation 200 wherein a newlyqueued information byte 41 is accessed. The sequence is repeated bycircuitry 81 unless an empty byte is detected by repeat inhibitcircuitry 82. If decision 202 determines that the significantinformation detected at decision 201 is not noted to be symbol notappear the information retrieved is understood to be either a blankspace on the page 14 or a symbol 12 that remains printed on the page 14from previous typing. In either event, the sequence proceeds tooperation 208 which simply issues a SPACE-COMMAND to typewriter l0 andthrough operation 207 advances the memory queue control 42 to the nexthigher order byte 41 in memory 40 before returning the sequence tooperation 200. The same operation occurs if decision 204 determines thatbyte 41 identified by decision 202 as containing symbol not appearinformation is determined by decision 204 to be simply a blank space onthe page 14 requiring simply operation 208 instead of the printsub-sequence beginning with decision 205. It can now be understood thatthe typewriter 10 responding to depression of the retype key willproceed incrementally along writing line 19 to reprint in order thosesymbols 12 previously erased but not deleted and will space over withoutreprinting any symbols l2 encountered which remain on the paper 14 fromprevious typing. This sequence is repeated until inhibited by circuitry82 at decision 201 which determines by interrogation of bit B10 in thebyte 41 placed in memory [/0 register 67 at operation 200 that nosignificant information remains at the current print point 13. Thesequence then is terminated by operation209 which resets the retypelatch 65 to its normal inactive condition.

While we have described a particular preferred illustrative embodimentemploying atypewriter 10 of specific configuration and the use ofpermanently wired electronic logic and memory units that operateaccording to preferred sequences, those skilled in the art willrecognize that various additions, deletions and modifi-' cations can bemade to the illustrative embodiment shown without departing from thenovel concept constituting our invention. Particularly it can beunderstood that our sequence could be programmed on a general purposecomputer connected with a printer provided with suitable print and erasemechanism. While the typewriter erase mechanism we have disclosed erasessymbols by reselecting the character to be erased, erasing devices suchas power driven rotary rubber erasers are known which can erase acharacter indiscriminately without a re-typing sequence and it isapparent to those skilled in the art that our control system canusefully be applied to typewriters having such erasing devices.Accordingly, the subject matter sought to be patented is to be definedsolely by the appended claims.

We claim:

1. In a system including a typewriter having means for printing visiblesymbols at a print point on a page, means for moving said print point toordered print positions along a line of the page, including backspacemeans for moving said print point incrementally to immediately adjacentlower order print positions, a keyboard that is manipulated to controlsaid symbol printing and print point moving means, signal output meansfor transmitting signals representative of typewriter operations, signalinput means for receiving control signals for causing operations of saidtypewriter, and selectively operable symbol erase mechanism operable inresponse to ERASE command signals, the improvement comprising:

a memory capable of storing a plurality of symbol informationidentifying bytes each corresponding with an individual print positionon a line of the page and each being at least capable of identifying thesymbol intended to appear in the corresponding print position,

queuing means for identifying individual ones of said bytes in saidmemory in accordance with the order of print positions with which saidbytes correspond,

keystroke recording control means responsive to manipulation of saidkeyboard and to said queuing means for writing a byte of symbolidentifying information into said memory and ordered therein inaccordance with its corresponding print position,

manually operable selection means including means to initiate an erasesequence erase sequence control means responsive to said erase sequenceinitiation for producing erase control operations and comprising: signalgenerating means for issuing next ERASE command signals to saidtypewriter, and erase sequence repeating means operating following eacherase control operation to cause operation of said typewriter backspacemeans, and producing a further one of said erase control operations.

2. A system as defined in claim 1 having the further improvementcomprising:

said erase sequence control means further including erase sequenceterminating means including means for detecting the completion of theerasure of all characters within a single word unit, and meansresponsive to said completion detecting means for inhibiting furtheroperation of said erase sequence repeating means.

3. A system as defined in claim 1 having the further improvementcomprising:

said erase sequence control means further including erase sequenceterminating means including means for detecting the completion of theerasure of all characters within a single line unit, and meansresponsive to said completion detecting means for inhibiting furtheroperation of said erase sequence repeating means.

4. A system as defined in claim 1 wherein the improvement furthercomprises:

said selection means including mode selecting means 1 having a firststate for defining an erase sequence of character" length and a secondstate for defining an erase sequence of word length.

said erase sequence control means further comprising erase sequenceterminating means including first detecting means for detecting thecompletion of the erasure of a single character, second detecting meansfor detecting the completion of the erasure of all characters within asingle word unit, and means responsive to said further mode selectingmeans and to said first and second detecting means for inhibitingfurther operation of said erase sequence repeating means upon thecompletion of the erasure of a single character when said further modeselecting means defines a character length erase sequence and uponcompletion of the erasure of all characters within a single word unitwhen said further mode selecting means defines a word length erasesequence.

5. A system as defined in claim 1 wherein the improvement furthercomprises:

said selection means including mode selecting means having a first statefor defining an erase sequence of character length and a second statefor defining erase sequence of word length and a third state fordefining an erase sequence of line length,

said erase sequence control means further comprising erase sequenceterminating means including first detecting means for detecting thecompletion of the erasure of a single character, second detecting meansfor detecting the completion of the erasure of all characters within asingle word unit, third detecting means for detecting the completion ofthe erasure of all characters within a single line unit and meansresponsive to said mode selecting means and to said first, second andthird detecting means for inhibiting further operation of said erasesequence repeating means upon the completion of the erasure of a singlecharacter when said mode selecting means defines a character lengtherase sequence, upon completion of the erasure of all characters withina single word unit when said mode selecting means defines a word lengtherase sequence, and upon completion of the erase of all characterswithin a single line unit when said mode selecting means defines a line"length erase sequence.

6. In a system including a typewriter having means for printing visiblesymbols at a print point on a page, means for moving said print point toordered print positions along a line of the page, a keyboard that ismanipulatable to control said symbol printing and print point movingmeans, signal output means for transmitting signals representative oftypewriter operations, signal input means for receiving control signalsfor causing operations of said typewriter, and selectively operablesymbol erase mechanism operable in response to ERASE command signals,the improvement comprising:

a memory capable of storing a plurality of symbol informationidentifying bytes, each corresponding with an individual print positionon a line of the page and each being at least capable of identifying (i)whether it contains useful information, (ii) the symbol intended toappear in the corresponding print position, and (iii) whether the symbolintended to appear in the corresponding print position currentlyappears, queuing means for identifying individual ones of said bytes insaid memory in accordance with the order of print positions with whichsaid bytes correspond,

keystroke recording control means responsive to manipulation of saidkeyboard and to said queuing means for writing a byte of symbolidentifying information into said memory and ordered therein inaccordance with its corresponding print position,

manually operable selection means including means to initiate an erasesequence and mode control means settable to define either an erase onlyoperation or an erase and delete operation of said erase sequence, and

erase sequence control means responsive to said erase sequenceinitiation for producing erase control operations and comprising: signalgenerating means for issuing said ERASE command signals to saidtypewriter, and memory writing means responsive to said mode controlmeans for selectively writing into the byte identified by said queuingmeans as corresponding with the relative print position from which saiderase mechanism erases a symbol in response to issuance of said ERASEcommand, symbol not appear if said erase only operation has been definedor no significant information" if said erase and delet operation hasbeen defined.

7. A. system as defined in claim 6 further comprising backspace meansfor moving said print point incrementally to immediately adjacent lowerorder print positions, and wherein the improvement further comprises:

said erase sequence control means including erase sequence repeatingmeans operating following each erase control operation to causeoperation of said typewriter backspace means and producing a further oneof said erase control operations.

8. A system as defined in claim 7, having the further improvementcomprising:

said erase sequence control means further including erase sequenceterminating means including means for detecting the completion of theerasure of all characters within a single word unit, and meansresponsive to said completion detecting means for inhibiting furtheroperation of said erase sequence repeating means.

9. A system as defined in claim 7, having the further improvementcomprising:

said erase sequence control means further including erase sequenceterminating means including means for detecting the completion of theerasure of all characters within a single line unit, and meansresponsive to said completion detecting means for inhibiting furtheroperation of said erase sequence repeating means.

10. A system as defined in claim 7 wherein the improvement furthercomprises:

said selection means including further mode selecting means havinga-first state for defining an erase sequence of character length and asecond state first detecting means for detecting the completion of theerasure of a single character, second detecting means for detecting thecompletion of the erasure of all characters within a single word unit,and means responsive to said further mode selecting means and to saidfirst and second detecting means for inhibiting further operation ofsaid erase sequence repeating means upon the completion of the erasureof a single character when said further mode selecting means defines acharacter length erase sequence and upon completion of the erasure ofall characters within a single word unit when said further modeselecting means defines a word" length erase sequence.

11. A system as defined in claim 7 wherein the improvement furthercomprises:

said selection means including further mode selecting means having afirst state for defining an erase sequence of character length and asecond state for defining erase sequence of word length and a thirdstate for defining an erase sequence of line length,

said erase sequence control means further comprising erase sequenceterminating means including first detecting means for detecting thecompletion of the erasure of a single character, second detecting meansfor detecting the completion of the erasure of all characters within asingle word unit, third detecting means for detecting the completion ofthe erasure of all characters within a single line unit and meansresponsive to said further mode selecting means and to said first,second and third detecting means for inhibiting further operation ofsaid erase sequence repeating means upon the completion of the erasureof a single character when said further mode selecting means defines acharacter length erase sequence, upon completion of the erasure of allcharacters within a single word unit when said further mode selectingmeans defines a word length erase sequence, and upon completion of theerase of all characters within a single line unit when said further modeselecting means defines a line length erase sequence.

12. A system as defined in claim 6 wherein the improvement furthercomprises:

manually operable retype selection means, retype sequence control meansoperable in response to activation of said retype selection means and tothe information contained within the memory byte identified by saidqueuing means corresponding with the current print position forproducing retype operations and comprising: means for operating saidtypewriter to reprint the symbol identified by said byte and advance theprint point to the next higher order print position in response todetection of symbol not appear information within said byte, and foroperating said typewriter to advance the print point to the next higherorder print position in response to detection of the presence of usefulinformation within said byte if said byte does not contain symbol notappear information.

13. A system as defined in claim 12 wherein said retype sequence controlmeans further comprises retype sequence repeating means operatingfollowing each advance of the print point and for producing a furtherone of said retype sequence control operations, and

19 retype terminating means for inhibiting operation of said retypesequence repeating means when said byte contains no useful information.14. A system as defined in claim 6, having the further improvementcomprising said erase sequence control means further comprising: memoryregression sequence control means responsive to selection of an eraseand delete operation of said erase sequence by said mode selecting meansfor successively regressing to a lower order, the bytes identified bysaid queuing means as being of a higher order than a byte into which hasbeen written no significant information. 15. A system as defined inclaim 6 wherein said improvement further comprises:

said keystroke recording control means further including memory advancesequence control means comprising means responsive to said queuing meansfor detecting the prior recording of information having symbol notappear information within the byte of said memory corresponding to thecurrent print position of the typewriter to advance to a higher orderthe byte corresponding to said current print position and those bytes ofhigher order than said current print position. 16. In a system includinga typewriter having means for printing visible symbols at a print pointon a page, means for moving said print point to ordered print positionsalong a line of the page, a keyboard that is manipulatable to controlsaid symbol printing and print point moving means, signal output meansfor transmitting signals representative of typewriter operations, signalinput means for receiving control signals for causing operations of saidtypewriter, and selectively operable symbol erase mechanism operable inresponse to an ERASE command signal, the improvement comprising:

a memory capable of storing a plurality of symbol informationidentifying bytes, each corresponding with an individual print positionon a line of the page and each being at least capable of identifying (i)whether it contains useful information, and (ii) the symbol intended toappear in the corresponding print position, queuing means foridentifying individual ones of said bytes in said memory in accordancewith the order of print positions with which said bytes correspond,

keystroke recording control means responsive to manipulation of saidkeyboard and to said queuing means for writing a byte of symbolidentifying information into said memory and ordered therein inaccordance with its corresponding print position,

manually operable selection means including means to initiate an erasesequence and mode control means settable to define either an erase onlyoperation or an erase and delete" operation of said erase sequence, and

erase sequence control means responsive to said erase sequenceinitiation for producing erase control operations and comprising: signalgenerating means for issuing said ERASE command signals to saidtypewriter, and memory writing means responsive to said mode controlmeans defining said erase and delete operation for writing nosignificant information" into the byte identified by said queuing meansas corresponding with the relative operations and comprising: means foroperating said typewriter to reprint the symbol identified by said byteand advance the print point to the next higher order print position.

18. A system as defined in claim 17 wherein said retype sequence controlmeans further comprises retype sequence repeating means operatingfollowing each advance of the print point and for producing a furtherone of said retype sequence control operations, and

retype terminating means for inhibiting operation of saidretype sequencerepeating means when said byte contains no useful information.

19. A system as defined in claim 16, having the fur-' ther improvementcomprising:

said erase sequence signal generating means further comprising: memoryregression sequence control means responsive to selection of an eraseand delete operation of said erase sequence by said mode selecting meansfor successively regressing to a lower order, the bytes identified bysaid queuing means as being of a higher order than a byte into which hasbeen written no significant information.

20. The method of operating a typewriter system including atypewritercapable of printing visible symbols in ordered print positions along awriting line, signal input means for receiving control signals forcausing operations of said typewriter, selectively operable symbol erasemechanism, a memory, addressing means for identifying symbol informationin individual bytes within said memory in accordance with said order ofprint positions, and mode selecting means for selecting either an eraseonly or an erase and delete operation comprising the steps of:

a. conditioning said erase mechanism to perform an erase operation uponreceipt of an ERASE command signal.

b. reading the symbol identifying byte from said memory corresponding tothe current print position of said typewriter,

issuing said ERASE command to effect an erase operation of said'erasemechanism to erase the symbol identified by the byte read from saidmemory, and writing symbol not appear information into the byte readfrom said memory if erase only operation is selected by said modeselecting means or writing no useful information into the byte read fromsaid memory if erase and delete operation is selected by said modeselecting means, d. backspacing the typewriter, e. regressing saidaddressing means by one,

f. repeating steps b, c, d, and e.

the current print position for producing retype I

1. In a system including a typewriter having means for printing visiblesymbols at a print point on a page, means for moving said print point toordered print positions along a line of the page, including backspacemeans for moving said print point incrementally to immediately adjacentlower order print positions, a keyboard that is manipulated to controlsaid symbol printing and print point moving means, signal output meansfor transmitting signals representative of tYpewriter operations, signalinput means for receiving control signals for causing operations of saidtypewriter, and selectively operable symbol erase mechanism operable inresponse to ERASE command signals, the improvement comprising: a memorycapable of storing a plurality of symbol information identifying byteseach corresponding with an individual print position on a line of thepage and each being at least capable of identifying the symbol intendedto appear in the corresponding print position, queuing means foridentifying individual ones of said bytes in said memory in accordancewith the order of print positions with which said bytes correspond,keystroke recording control means responsive to manipulation of saidkeyboard and to said queuing means for writing a byte of symbolidentifying information into said memory and ordered therein inaccordance with its corresponding print position, manually operableselection means including means to initiate an erase sequence erasesequence control means responsive to said erase sequence initiation forproducing erase control operations and comprising: signal generatingmeans for issuing next ERASE command signals to said typewriter, anderase sequence repeating means operating following each erase controloperation to cause operation of said typewriter backspace means, andproducing a further one of said erase control operations.
 2. A system asdefined in claim 1 having the further improvement comprising: said erasesequence control means further including erase sequence terminatingmeans including means for detecting the completion of the erasure of allcharacters within a single word unit, and means responsive to saidcompletion detecting means for inhibiting further operation of saiderase sequence repeating means.
 3. A system as defined in claim 1 havingthe further improvement comprising: said erase sequence control meansfurther including erase sequence terminating means including means fordetecting the completion of the erasure of all characters within asingle line unit, and means responsive to said completion detectingmeans for inhibiting further operation of said erase sequence repeatingmeans.
 4. A system as defined in claim 1 wherein the improvement furthercomprises: said selection means including mode selecting means having afirst state for defining an erase sequence of ''''character'''' lengthand a second state for defining an erase sequence of ''''word''''length. said erase sequence control means further comprising erasesequence terminating means including first detecting means for detectingthe completion of the erasure of a single character, second detectingmeans for detecting the completion of the erasure of all characterswithin a single word unit, and means responsive to said further modeselecting means and to said first and second detecting means forinhibiting further operation of said erase sequence repeating means uponthe completion of the erasure of a single character when said furthermode selecting means defines a ''''character'''' length erase sequenceand upon completion of the erasure of all characters within a singleword unit when said further mode selecting means defines a ''''word''''length erase sequence.
 5. A system as defined in claim 1 wherein theimprovement further comprises: said selection means including modeselecting means having a first state for defining an erase sequence of''''character'''' length and a second state for defining erase sequenceof ''''word'''' length and a third state for defining an erase sequenceof ''''line'''' length, said erase sequence control means furthercomprising erase sequence terminating means including first detectingmeans for detecting the completion of the erasure of a single character,second detecting means for detecting the completion of the erasure ofall characters within a single word unit, third detecting means fordetecting the completion of tHe erasure of all characters within asingle line unit and means responsive to said mode selecting means andto said first, second and third detecting means for inhibiting furtheroperation of said erase sequence repeating means upon the completion ofthe erasure of a single character when said mode selecting means definesa ''''character'''' length erase sequence, upon completion of theerasure of all characters within a single ''''word'''' unit when saidmode selecting means defines a ''''word'''' length erase sequence, andupon completion of the erase of all characters within a single line unitwhen said mode selecting means defines a ''''line'''' length erasesequence.
 6. In a system including a typewriter having means forprinting visible symbols at a print point on a page, means for movingsaid print point to ordered print positions along a line of the page, akeyboard that is manipulatable to control said symbol printing and printpoint moving means, signal output means for transmitting signalsrepresentative of typewriter operations, signal input means forreceiving control signals for causing operations of said typewriter, andselectively operable symbol erase mechanism operable in response toERASE command signals, the improvement comprising: a memory capable ofstoring a plurality of symbol information identifying bytes, eachcorresponding with an individual print position on a line of the pageand each being at least capable of identifying (i) whether it containsuseful information, (ii) the symbol intended to appear in thecorresponding print position, and (iii) whether the symbol intended toappear in the corresponding print position currently appears, queuingmeans for identifying individual ones of said bytes in said memory inaccordance with the order of print positions with which said bytescorrespond, keystroke recording control means responsive to manipulationof said keyboard and to said queuing means for writing a byte of symbolidentifying information into said memory and ordered therein inaccordance with its corresponding print position, manually operableselection means including means to initiate an erase sequence and modecontrol means settable to define either an ''''erase only'''' operationor an ''''erase and delete'''' operation of said erase sequence, anderase sequence control means responsive to said erase sequenceinitiation for producing erase control operations and comprising: signalgenerating means for issuing said ERASE command signals to saidtypewriter, and memory writing means responsive to said mode controlmeans for selectively writing into the byte identified by said queuingmeans as corresponding with the relative print position from which saiderase mechanism erases a symbol in response to issuance of said ERASEcommand, ''''symbol not appear'''' if said ''''erase only'''' operationhas been defined or ''''no significant information'''' if said ''''eraseand delet'''' operation has been defined.
 7. A. system as defined inclaim 6 further comprising backspace means for moving said print pointincrementally to immediately adjacent lower order print positions, andwherein the improvement further comprises: said erase sequence controlmeans including erase sequence repeating means operating following eacherase control operation to cause operation of said typewriter backspacemeans and producing a further one of said erase control operations.
 8. Asystem as defined in claim 7, having the further improvement comprising:said erase sequence control means further including erase sequenceterminating means including means for detecting the completion of theerasure of all characters within a single word unit, and meansresponsive to said completion detecting means for inhibiting furtheroperation of said erase sequence repeating means.
 9. A system as definedin claim 7, having the further improvement comprising: said erasesequence control means further including eRase sequence terminatingmeans including means for detecting the completion of the erasure of allcharacters within a single line unit, and means responsive to saidcompletion detecting means for inhibiting further operation of saiderase sequence repeating means.
 10. A system as defined in claim 7wherein the improvement further comprises: said selection meansincluding further mode selecting means having a first state for definingan erase sequence of ''''character'''' length and a second state fordefining an erase sequence of ''''word'''' length, said erase sequencecontrol means further comprising erase sequence terminating meansincluding first detecting means for detecting the completion of theerasure of a single character, second detecting means for detecting thecompletion of the erasure of all characters within a single word unit,and means responsive to said further mode selecting means and to saidfirst and second detecting means for inhibiting further operation ofsaid erase sequence repeating means upon the completion of the erasureof a single character when said further mode selecting means defines a''''character'''' length erase sequence and upon completion of theerasure of all characters within a single word unit when said furthermode selecting means defines a ''''word'''' length erase sequence.
 11. Asystem as defined in claim 7 wherein the improvement further comprises:said selection means including further mode selecting means having afirst state for defining an erase sequence of ''''character'''' lengthand a second state for defining erase sequence of ''''word'''' lengthand a third state for defining an erase sequence of ''''line'''' length,said erase sequence control means further comprising erase sequenceterminating means including first detecting means for detecting thecompletion of the erasure of a single character, second detecting meansfor detecting the completion of the erasure of all characters within asingle word unit, third detecting means for detecting the completion ofthe erasure of all characters within a single line unit and meansresponsive to said further mode selecting means and to said first,second and third detecting means for inhibiting further operation ofsaid erase sequence repeating means upon the completion of the erasureof a single character when said further mode selecting means defines a''''character'''' length erase sequence, upon completion of the erasureof all characters within a single word unit when said further modeselecting means defines a ''''word'''' length erase sequence, and uponcompletion of the erase of all characters within a single line unit whensaid further mode selecting means defines a ''''line'''' length erasesequence.
 12. A system as defined in claim 6 wherein the improvementfurther comprises: manually operable retype selection means, retypesequence control means operable in response to activation of said retypeselection means and to the information contained within the memory byteidentified by said queuing means corresponding with the current printposition for producing retype operations and comprising: means foroperating said typewriter to reprint the symbol identified by said byteand advance the print point to the next higher order print position inresponse to detection of ''''symbol not appear'''' information withinsaid byte, and for operating said typewriter to advance the print pointto the next higher order print position in response to detection of thepresence of useful information within said byte if said byte does notcontain ''''symbol not appear'''' information.
 13. A system as definedin claim 12 wherein said retype sequence control means further comprisesretype sequence repeating means operating following each advance of theprint point and for producing a further one of said retype sequencecontrol operations, and retype terminating means for inhibitingoperation of said retype sequence repeatIng means when said bytecontains no useful information.
 14. A system as defined in claim 6,having the further improvement comprising said erase sequence controlmeans further comprising: memory regression sequence control meansresponsive to selection of an ''''erase and delete'''' operation of saiderase sequence by said mode selecting means for successively regressingto a lower order, the bytes identified by said queuing means as being ofa higher order than a byte into which has been written ''''nosignificant information.''''
 15. A system as defined in claim 6 whereinsaid improvement further comprises: said keystroke recording controlmeans further including memory advance sequence control means comprisingmeans responsive to said queuing means for detecting the prior recordingof information having ''''symbol not appear'''' information within thebyte of said memory corresponding to the current print position of thetypewriter to advance to a higher order the byte corresponding to saidcurrent print position and those bytes of higher order than said currentprint position.
 16. In a system including a typewriter having means forprinting visible symbols at a print point on a page, means for movingsaid print point to ordered print positions along a line of the page, akeyboard that is manipulatable to control said symbol printing and printpoint moving means, signal output means for transmitting signalsrepresentative of typewriter operations, signal input means forreceiving control signals for causing operations of said typewriter, andselectively operable symbol erase mechanism operable in response to anERASE command signal, the improvement comprising: a memory capable ofstoring a plurality of symbol information identifying bytes, eachcorresponding with an individual print position on a line of the pageand each being at least capable of identifying (i) whether it containsuseful information, and (ii) the symbol intended to appear in thecorresponding print position, queuing means for identifying individualones of said bytes in said memory in accordance with the order of printpositions with which said bytes correspond, keystroke recording controlmeans responsive to manipulation of said keyboard and to said queuingmeans for writing a byte of symbol identifying information into saidmemory and ordered therein in accordance with its corresponding printposition, manually operable selection means including means to initiatean erase sequence and mode control means settable to define either an''''erase only'''' operation or an ''''erase and delete'''' operation ofsaid erase sequence, and erase sequence control means responsive to saiderase sequence initiation for producing erase control operations andcomprising: signal generating means for issuing said ERASE commandsignals to said typewriter, and memory writing means responsive to saidmode control means defining said ''''erase and delete'''' operation forwriting ''''no significant information'''' into the byte identified bysaid queuing means as corresponding with the relative print positionfrom which said erase mechanism erases a symbol.
 17. A system as definedin claim 16 wherein the improvement further comprises: manually operableretype selection means, retype sequence control means operable inresponse to activation of said retype selection means and to theinformation contained within the memory byte identified by said queuingmeans corresponding with the current print position for producing retypeoperations and comprising: means for operating said typewriter toreprint the symbol identified by said byte and advance the print pointto the next higher order print position.
 18. A system as defined inclaim 17 wherein said retype sequence control means further comprisesretype sequence repeating means operating following each advance of theprint point and for producing a further one of said retype sequencecontrol operations, and retype terminating means for inhibitingoperation of said retype sequence repeating means when said bytecontains no useful information.
 19. A system as defined in claim 16,having the further improvement comprising: said erase sequence signalgenerating means further comprising: memory regression sequence controlmeans responsive to selection of an ''''erase and delete'''' operationof said erase sequence by said mode selecting means for successivelyregressing to a lower order, the bytes identified by said queuing meansas being of a higher order than a byte into which has been written''''no significant information.''''
 20. The method of operating atypewriter system including a typewriter capable of printing visiblesymbols in ordered print positions along a writing line, signal inputmeans for receiving control signals for causing operations of saidtypewriter, selectively operable symbol erase mechanism, a memory,addressing means for identifying symbol information in individual byteswithin said memory in accordance with said order of print positions, andmode selecting means for selecting either an ''''erase only'''' or an''''erase and delete'''' operation comprising the steps of: a.conditioning said erase mechanism to perform an erase operation uponreceipt of an ERASE command signal. b. reading the symbol identifyingbyte from said memory corresponding to the current print position ofsaid typewriter, c. issuing said ERASE command to effect an eraseoperation of said erase mechanism to erase the symbol identified by thebyte read from said memory, and writing ''''symbol not appear''''information into the byte read from said memory if ''''erase only''''operation is selected by said mode selecting means or writing ''''nouseful information'''' into the byte read from said memory if ''''eraseand delete'''' operation is selected by said mode selecting means, d.backspacing the typewriter, e. regressing said addressing means by one,f. repeating steps b, c, d, and e.